The present proposal is addressed to the mechanism by which calcium fluxes into and out of sarcoplasmic reticulum are controlled. The mechanisms underlying the transitions between calcium influx and efflux in SR will be studied. Effects of various ionophores and drugs, including local anaesthetic agents will be examined. The role of lipids, including fatty acids, cholesterol and phospholipids will be studied in terms of both calcium influx and calcium efflux.